Oxygen sensor

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Oxygen sensor (2006-2012)

• Introduction– Before the extinction level event in Japanese

vacuum-technology-based manufacturing industries in 200X, the detection of trace amounts (e.g., 10-9, 10-12, 10-15, …) of oxygen had been gaining increasing attention.

– As the key device for in-situ monitoring trace levels of oxygen, one kind of sensor had been focused.

– Our R&D project was subsidized by the government and the company.

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• What’s new?– Measuring procedure:• To desorb oxygen from an n-type semiconductor surface by

ultraviolet(UV) light irradiation.• To adsorb oxygen onto the semiconductor surface after turning the UV-light off.• To measure electrical resistance of the n-type

semiconductor surface.Time Chart

UV

Mea

e.g., 1 sec

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• What’s new?– Measuring procedure:

Time Chart

UV

Interaction between oxygen and n-type semiconductor

Ec

Ev

NOMO(O2-)

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• What’s new?– To use ultrathin film with the thickness being – comparable with polaron diameter: ( Large Low conc. O2 )

6 TiO6 units at PO2=10-20

5 TiO6 units at PO2=10-9

( Small High conc. O2 )

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• What’s new?– To use ultrathin film with the thickness being

comparable with polaron diameter:

Polaron diameter

Larger polaron diameter:Higher conductance(Lower resistance)

Smaller polaron diameter:Lower conductance(Higher resistance)

Film thickness

TiO6 unit cell

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• What’s new?– Hypothetical image:

Although SrTiO3 is

paraelectric, near the surface of STOadsorbed oxygen can (?)induce the ferroelectric-likeIonic displacement.

O

Sr

Sr

O

O

Sr

Sr

O

Sr

Sr

O

O

O e

Ti

O

Ti

O

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• What’s new?– Only paraelectric perovskites can show oxygen-

concentration-sensitive electrical resistance.

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• Performance:

1.0E+08

1.0E+10

1.0E+12

1.0E+14

1.E-15 1.E-10 1.E-05 1.E+00

Res

ista

nce

(Ω

)

Oxygen concentration ( PO2 / (PO2 + PHe) )

108

10010-15

1014

1012

1010

10-10 10-5

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http://toruhara.page.tl/2-.--Solid_Gas-Interface.htm



Oxygen sensor

Engineering

Transcript of Oxygen sensor